Omni-band amplifiers

ABSTRACT

Omni-band amplifiers supporting multiple band groups are disclosed. In an exemplary design, an apparatus (e.g., a wireless device, an integrated circuit, etc.) includes at least one gain transistor and a plurality of cascode transistors for a plurality of band groups. Each band group covers a plurality of bands. The gain transistor(s) receive an input radio frequency (RF) signal. The cascode transistors are coupled to the gain transistor(s) and provide an output RF signal for one of the plurality of band groups. In an exemplary design, the gain transistor(s) include a plurality of gain transistors for the plurality of band groups. One gain transistor and one cascode transistor are enabled to amplify the input RF signal and provide the output RF signal for the selected band group. The gain transistors may be coupled to different taps of a single source degeneration inductor or to different source degeneration inductors.

BACKGROUND

I. Field

The present disclosure relates generally to electronics, and morespecifically to amplifiers.

II. Background

A wireless device (e.g., a cellular phone or a smartphone) in a wirelesscommunication system may transmit and receive data for two-waycommunication. The wireless device may include a transmitter for datatransmission and a receiver for data reception. For data transmission,the transmitter may modulate a radio frequency (RF) carrier signal withdata to obtain a modulated RF signal, amplify the modulated RF signal toobtain an amplified RF signal having the proper output power level, andtransmit the amplified RF signal via an antenna to a base station. Fordata reception, the receiver may obtain a received RF signal via theantenna and may amplify and process the received RF signal to recoverdata sent by the base station.

A wireless device may support operation over a wide frequency range. Thewireless device may include a number of amplifiers, with each amplifierbeing designed to operate over a portion of the wide frequency rangesupported by the wireless device. It is desirable to support operationover a wide frequency range with as few amplifiers as possible.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a wireless device communicating with a wireless system.

FIG. 2 shows three exemplary band groups.

FIG. 3 shows a block diagram of the wireless device in FIG. 1.

FIGS. 4A to 4D show an omni-band low noise amplifier (LNA) with a sharedsource degeneration inductor.

FIG. 5 shows an omni-band LNA with separate source degenerationinductors.

FIG. 6 shows an omni-band LNA without a source degeneration inductor.

FIG. 7 shows an omni-band LNA with a shared source degeneration inductorand feedback.

FIG. 8 shows an omni-band LNA with a tunable matching circuit.

FIGS. 9A to 6F shows six exemplary designs of a tunable matchingcircuit.

FIG. 10 shows a top view of three transformers for three band groups.

FIG. 11 shows a process for performing signal amplification.

DETAILED DESCRIPTION

The detailed description set forth below is intended as a description ofexemplary designs of the present disclosure and is not intended torepresent the only designs in which the present disclosure can bepracticed. The term “exemplary” is used herein to mean “serving as anexample, instance, or illustration.” Any design described herein as“exemplary” is not necessarily to be construed as preferred oradvantageous over other designs. The detailed description includesspecific details for the purpose of providing a thorough understandingof the exemplary designs of the present disclosure. It will be apparentto those skilled in the art that the exemplary designs described hereinmay be practiced without these specific details. In some instances,well-known structures and devices are shown in block diagram form inorder to avoid obscuring the novelty of the exemplary designs presentedherein.

Omni-band amplifiers supporting a wide frequency range covering multipleband groups are disclosed herein. The omni-band amplifiers may also bereferred to as universal amplifiers, etc. The omni-band amplifiers maybe used for various types of electronic devices such as wirelesscommunication devices.

FIG. 1 shows a wireless device 110 communicating with a wirelesscommunication system 120. Wireless system 120 may be a Long TermEvolution (LTE) system, a Code Division Multiple Access (CDMA) system, aGlobal System for Mobile Communications (GSM) system, a wireless localarea network (WLAN) system, or some other wireless system. A CDMA systemmay implement Wideband CDMA (WCDMA), CDMA 1X, Evolution-Data Optimized(EVDO), Time Division Synchronous CDMA (TD-SCDMA), or some other versionof CDMA. For simplicity, FIG. 1 shows wireless system 120 including twobase stations 130 and 132 and one system controller 140. In general, awireless system may include any number of base stations and any set ofnetwork entities.

Wireless device 110 may also be referred to as a user equipment (UE), amobile station, a terminal, an access terminal, a subscriber unit, astation, etc. Wireless device 110 may be a cellular phone, a smartphone,a tablet, a wireless modem, a personal digital assistant (PDA), ahandheld device, a laptop computer, a smartbook, a netbook, a cordlessphone, a wireless local loop (WLL) station, a Bluetooth device, etc.Wireless device 110 may communicate with wireless system 120. Wirelessdevice 110 may also receive signals from broadcast stations (e.g., abroadcast station 134), signals from satellites (e.g., a satellite 150)in one or more global navigation satellite systems (GNSS), etc. Wirelessdevice 110 may support one or more radio technologies for wirelesscommunication such as LTE, WCDMA, CDMA 1X, EVDO, TD-SCDMA, GSM, 802.11,etc.

FIG. 2 shows three exemplary band groups that may be supported bywireless device 110. Wireless device 110 may be able to operate inlow-band (LB) covering frequencies lower than 1000 megahertz (MHz),mid-band (MB) covering frequencies from 1000 MHz to 2300 MHz, and/orhigh-band (HB) covering frequencies higher than 2300 MHz. For example,low-band may cover 698 to 960 MHz, mid-band may cover 1475 to 2170 MHz,and high-band may cover 2300 to 2690 MHz and 3400 to 3800 MHz, as shownin FIG. 2. Low-band, mid-band, and high-band refer to three groups ofbands (or band groups), with each band group including a number offrequency bands (or simply, “bands”). Each band may cover up to 200 MHz.LTE Release 11 supports 35 bands, which are referred to as LTE/UMTSbands and are listed in 3GPP TS 36.101.

In general, any number of band groups may be defined. Each band groupmay cover any range of frequencies, which may or may not match any ofthe frequency ranges shown in FIG. 2. Each band group may also includeany number of bands.

FIG. 3 shows a block diagram of an exemplary design of wireless device110 in FIG. 1. In this exemplary design, wireless device 110 includes atransceiver 320 coupled to a primary antenna 310, a transceiver 322coupled to a secondary antenna 312, and a data processor/controller 380.Transceiver 320 includes multiple (K) receivers 330 pa to 330 pk andmultiple (K) transmitters 350 pa to 350 pk to support multiple frequencybands, multiple radio technologies, carrier aggregation, etc.Transceiver 322 includes L receivers 330 sa to 330 sl and L transmitters350 sa to 350 sl to support multiple frequency bands, multiple radiotechnologies, carrier aggregation, receive diversity, multiple-inputmultiple-output (MIMO) transmission from multiple transmit antennas tomultiple receive antennas, etc.

In the exemplary design shown in FIG. 3, each receiver 330 includes anLNA 340 and receive circuits 342. For data reception, antenna 310receives signals from base stations and/or other transmitter stationsand provides a received RF signal, which is routed through an antennainterface circuit 324 and presented as an input RF signal to a selectedreceiver. Antenna interface circuit 324 may include switches, duplexers,transmit filters, receive filters, matching circuits, etc. Thedescription below assumes that receiver 330 pa is the selected receiver.Within receiver 330 pa, an LNA 340 pa amplifies the input RF signal andprovides an output RF signal. Receive circuits 342 pa downconvert theoutput RF signal from RF to baseband, amplify and filter thedownconverted signal, and provide an analog input signal to dataprocessor 380. Receive circuits 342 pa may include mixers, filters,amplifiers, matching circuits, an oscillator, a local oscillator (LO)generator, a phase locked loop (PLL), etc. Each remaining receiver 330in transceivers 320 and 322 may operate in similar manner as receiver330 pa.

In the exemplary design shown in FIG. 3, each transmitter 350 includestransmit circuits 352 and a power amplifier (PA) 354. For datatransmission, data processor 380 processes (e.g., encodes and modulates)data to be transmitted and provides an analog output signal to aselected transmitter. The description below assumes that transmitter 350pa is the selected transmitter. Within transmitter 350 pa, transmitcircuits 352 pa amplify, filter, and upconvert the analog output signalfrom baseband to RF and provide a modulated RF signal. Transmit circuits352 pa may include amplifiers, filters, mixers, matching circuits, anoscillator, an LO generator, a PLL, etc. A PA 354 pa receives andamplifies the modulated RF signal and provides a transmit RF signalhaving the proper output power level. The transmit RF signal is routedthrough antenna interface circuit 324 and transmitted via antenna 310.Each remaining transmitter 350 in transceivers 320 and 322 may operatein similar manner as transmitter 350 pa.

FIG. 3 shows an exemplary design of receiver 330 and transmitter 350. Areceiver and a transmitter may also include other circuits not shown inFIG. 3, such as filters, matching circuits, etc. All or a portion oftransceivers 320 and 322 may be implemented on one or more analogintegrated circuits (ICs), RF ICs (RFICs), mixed-signal ICs, etc. Forexample, LNAs 340 and receive circuits 342 may be implemented on onemodule, which may be an RFIC, etc. The circuits in transceivers 320 and322 may also be implemented in other manners.

Data processor/controller 380 may perform various functions for wirelessdevice 110. For example, data processor 380 may perform processing fordata being received via receivers 330 and data being transmitted viatransmitters 350. Controller 380 may control the operation of thevarious circuits within transceivers 320 and 322. A memory 382 may storeprogram codes and data for data processor/controller 380. Dataprocessor/controller 380 may be implemented on one or more applicationspecific integrated circuits (ASICs) and/or other ICs.

Wireless device 110 may support multiple band groups, multiple radiotechnologies, and/or multiple antennas. Wireless device 110 may includea number of LNAs to support reception via the multiple band groups,multiple radio technologies, and/or multiple antennas.

In an aspect of the present disclosure, omni-band LNAs may be used tosupport reception via multiple band groups. An omni-band LNA is an LNAthat supports multiple band groups and has (i) a single input for allsupported band groups and (ii) multiple outputs for the multiple bandgroups, e.g., one output for each band group. An omni-band LNA mayreceive an input RF signal at its input and provide an output RF signalat one of its multiple outputs. An omni-band LNA covers multiple bandgroups and is different from a multi-band LNA that covers multiple bandsin the same band group.

Omni-band LNAs may be implemented with various circuit designs. Someexemplary designs of omni-band LNAs are described below. Omni-band LNAsmay also be implemented with transistors of various types. Someexemplary designs of omni-band LNAs implemented with N-channel metaloxide semiconductor (NMOS) transistors are described below.

FIG. 4A shows a schematic diagram of an exemplary design of an omni-bandLNA 440 with a shared source degeneration inductor. Omni-band LNA 440may be used for any one of LNAs 340 in FIG. 3. In the exemplary designshown in FIG. 4A, omni-band LNA 440 includes three amplifier circuits450 a, 450 b and 450 c for three band groups of low-band, mid-band andhigh-band, respectively.

In the exemplary design shown in FIG. 4A, each amplifier circuit 450includes a gain transistor 454 coupled to a cascode transistor 456 andalso to a multi-tap source degeneration inductor 452. Within amplifiercircuit 450 a for low-band, a gain transistor 454 a has its gatereceiving an input RF signal (RFin) and its source coupled to one end ofmulti-tap inductor 452. Multi-tap inductor 452 has four taps A, B, C andD, with taps A and D corresponding to the two ends of inductor 452.Inductor 452 has tap A coupled to the source of gain transistor 454 aand tap D coupled to circuit ground. A cascode transistor 456 a has itssource coupled to the drain of gain transistor 454 a, its gate receivinga first enable control signal (Venb1) for low-band, and its draincoupled to an output of amplifier circuit 450 a.

Amplifier circuit 450 b for mid-band includes a gain transistor 454 band a cascode transistor 456 b, which are coupled in similar manner asgain transistor 454 a and cascode transistor 456 a in amplifier circuit450 a for low-band. Amplifier circuit 450 c for high-band includes again transistor 454 c and a cascode transistor 456 c, which are alsocoupled in similar manner as gain transistor 454 a and cascodetransistor 456 a in amplifier circuit 450 a for low-band. The source ofgain transistor 454 b for mid-band is coupled to tap B of multi-tapinductor 452, and the source of gain transistor 454 c for high-band iscoupled to tap C of multi-tap inductor 452. Gain transistors 454 a to454 c and cascode transistors 456 a to 456 c may be implemented withNMOS transistors, as shown in FIG. 4A, or with transistors of othertypes.

Inductor 452 serves as source degeneration inductors for all three gaintransistors 454 a, 454 b and 454 c, which observe progressively smallersource inductances due to their connection at different taps of inductor452. In particular, gain transistor 454 c for high-band is coupled totap C, which is closest to circuit ground, and hence observes thesmallest source degeneration inductance. Gain transistor 454 b formid-band is coupled to higher tap B and hence observes a larger sourcedegeneration inductance. Gain transistor 454 a for low-band is coupledto the top end of inductor 452 at tap A and hence observes the largestsource degeneration inductance.

In the exemplary design shown in FIG. 4A, a variable capacitor 458 maybe present across the gate and source of gain transistor 454 a.Capacitor 458 may include parasitic capacitance of gain transistors 454a, 454 b and 454 c. Capacitor 458 may also include a bank of switchablecapacitors, which may be coupled between the gate and source of gaintransistor 454 a and may be used to fine-tune the input impedance ofomni-band LNA 440. Each switchable capacitor may be implemented with acapacitor coupled in series with a switch. The capacitors in the bankmay be selected to obtain good input matching for omni-band LNA 440.

Amplifier circuits 450 a, 450 b and 450 c are coupled to three loadcircuits 470 a, 470 b and 470 c, respectively. In the exemplary designshown in FIG. 4A, each load circuit 470 includes a transformer 472comprising a primary coil 474 and a secondary coil 476. A coil may alsobe referred to as an inductor coil, a winding, a conductor, etc. Withinload circuit 470 a for low-band, a transformer 472 a includes (i) aprimary coil 474 a coupled between the output of amplifier circuit 450 aand a power supply (VDD) and (ii) a secondary coil 476 a providing afirst differential amplified RF signal (RFamp1) to a downconverter forlow-band (not shown in FIG. 4A). Load circuit 470 b for mid-bandincludes a transformer 472 b having (i) a primary coil 474 b coupledbetween the output of amplifier circuit 450 b and the VDD supply and(ii) a secondary coil 476 b providing a second differential amplified RFsignal (RFamp2) to a downconverter for mid-band (not shown in FIG. 4A).Load circuit 470 c for high-band includes a transformer 472 c having (i)a primary coil 474 c coupled between the output of amplifier circuit 450c and the VDD supply and (ii) a secondary coil 476 c providing a thirddifferential amplified RF signal (RFamp3) to a downconverter forhigh-band (not shown in FIG. 4A). Transformers 472 a, 472 b and 472 care coupled to the drains of cascode transistors 456 a, 456 b and 456 c,respectively. Transformers 472 a, 472 b and 472 c may be designed toprovide good performance for low-band, mid-band, and high-band,respectively.

In one exemplary design, each load circuit 470 may be coupled to aseparate downconverter. In another exemplary design, multiple loadcircuits 470 may be coupled to a shared downconverter via switches. Theswitches may be controlled to pass an amplified RF signal from one loadcircuit to the shared downconverter at any given moment. For bothexemplary designs, each downconverter may include two mixers to performquadrature downconversion of an amplified RF signal from RF to eitherbaseband or an intermediate frequency (IF).

Load circuits 470 may also be implemented in other manners. In anotherexemplary design, a load circuit may include an inductor and possibly acapacitor coupled between the output of an amplifier circuit and the VDDsupply. In yet another exemplary design, a load circuit may include aP-channel metal oxide semiconductor (PMOS) transistor having its sourcecoupled to the VDD supply and its drain coupled to the drain of acascode transistor 456. The PMOS transistor may provide an active loadfor cascode transistor 456.

Amplifier circuits 450 a, 450 b and 450 c may be implemented in variousmanners. In an exemplary design, gain transistors 454 a, 454 b and 454 cmay have similar transistor sizes, and cascode transistors 456 a, 456 band 456 c may also have similar transistor sizes. In another exemplarydesign, gain transistors 454 a, 454 b and 454 c may have differenttransistor sizes and/or cascode transistors 456 a, 456 b and 456 c mayhave different transistor sizes. In an exemplary design, gaintransistors 454 a, 454 b and 454 c may have similar bias currents, whichmay be selected to provide good performance for all three band groups.In another exemplary design, gain transistors 454 a, 454 b and 454 c mayhave different bias currents. The bias current for each gain transistor454 may be selected to provide good performance for the associated bandgroup.

FIG. 4A shows omni-band LNA 440 including three amplifier circuits 450a, 450 b and 450 c for three band groups. An omni-band LNA may includefewer or more than three amplifier circuits 450 for fewer or more bandgroups.

Omni-band LNA 440 receives an input RF signal, which is applied to allthree amplifier circuits 450 a, 450 b and 450 c. The input RF signal mayinclude one or more transmissions in one or more bands in a band groupof interest, i.e., a selected band group. The amplifier circuit 450 forthe selected band group may be enabled to amplify the input RF signaland provide an output RF signal for the selected band group. Loadcircuit 470 for the selected band group may receive the output RF signalfrom the enabled amplifier circuit 450 and provide an amplified RFsignal for the selected band group. The remaining amplifier circuits 450for other band groups may be disabled.

FIG. 4B shows operation of omni-band LNA 440 when low-band is selected.In this case, amplifier circuit 450 a is enabled to generate a firstoutput RF signal (RFout1) for low-band by providing an appropriate biasvoltage on the Venb1 signal at the gate of cascode transistor 456 a.Load circuit 470 a receives the RFout1 signal and provides the RFamp1signal for low-band to a downconverter. Gain transistor 454 a observes alarge source degeneration inductance via the entire inductor 452.Amplifier circuits 450 b and 450 c are disabled by providing lowvoltages on the Venb2 and Venb3 signals at the gates of cascodetransistors 456 b and 456 c, respectively.

FIG. 4C shows operation of omni-band LNA 440 when mid-band is selected.In this case, amplifier circuit 450 b is enabled to generate a secondoutput RF signal (RFout2) for mid-band by providing an appropriate biasvoltage on the Venb2 signal at the gate of cascode transistor 456 b.Load circuit 470 b receives the RFout2 signal and provides the RFamp2signal for mid-band to a downconverter. Gain transistor 454 b observes amedium source degeneration inductance via a portion of inductor 452 fromtap B to circuit ground. Amplifier circuits 450 a and 450 c are disabledby providing low voltages on the Venb1 and Venb3 signals at the gates ofcascode transistors 456 a and 456 c, respectively.

FIG. 4D shows operation of omni-band LNA 440 when high-band is selected.

In this case, amplifier circuit 450 c is enabled to generate a thirdoutput RF signal (RFout3) for high-band by providing an appropriate biasvoltage on the Venb3 signal at the gate of cascode transistor 456 c.Load circuit 470 c receives the RFout3 signal and provides the RFamp3signal for high-band to a downconverter. Gain transistor 454 c observesa small source degeneration inductance via a portion of inductor 452from tap C to circuit ground. Amplifier circuits 450 a and 450 b aredisabled by providing low voltages on the Venb1 and Venb2 signals at thegates of cascode transistors 456 a and 456 b, respectively.

In an exemplary design, a gain transistor in an amplifier circuit mayoperate in (i) a saturation region when the amplifier circuit is enabledor (ii) a linear region when the amplifier circuit is disabled.Operating the gain transistor in the linear region when the amplifiercircuit is disabled may reduce changes in the input impedance ofomni-band LNA 440 regardless of which amplifier circuit or band group isselected. The input capacitance (C_(IN)) of a gain transistor may beexpressed as:

$\begin{matrix}{{C_{IN} = {{\frac{2}{3} \cdot W \cdot L \cdot C_{OX}}\mspace{14mu} {when}\mspace{14mu} {the}\mspace{14mu} {amplifier}\mspace{14mu} {circuit}\mspace{14mu} {is}\mspace{14mu} {enabled}}},\; {and}} & {{Eq}\mspace{14mu} (1)} \\{{C_{IN} = {{\frac{1}{2} \cdot W \cdot L \cdot C_{OX}}\mspace{14mu} {when}\mspace{14mu} {the}\mspace{14mu} {amplifier}\mspace{14mu} {circuit}\mspace{14mu} {is}\mspace{14mu} {disabled}}},} & {{Eq}\mspace{14mu} (2)}\end{matrix}$

where W is the width and L is the length of the gain transistor, and

C_(OX) is a gate oxide capacitance of the gain transistor.

As shown in equations (1) and (2), there may be a finite change in theinput impedance of a gain transistor depending on whether an amplifiercircuit is enabled or disabled. However, the input impedance ofomni-band LNA 440 may be maintained within tolerable limits regardlessof which amplifier circuit is selected and even with the change in theinput impedance of the gain transistor. Maintaining the input impedanceof omni-band LNA 440 within tolerable limits may improve power and/orimpedance matching for all band groups.

FIG. 5 shows a schematic diagram of an exemplary design of an omni-bandLNA 540 with separate source degeneration inductors. Omni-band LNA 540may also be used for any one of LNAs 340 in FIG. 3. In the exemplarydesign shown in FIG. 5, omni-band LNA 540 includes three amplifiercircuits 550 a, 550 b and 550 c for low-band, mid-band, and high-band,respectively. Each amplifier circuit 550 includes a gain transistor 554coupled to a cascode transistor 556 and also to a source degenerationinductor 552. Within amplifier circuit 550 a for low-band, a gaintransistor 554 a has its gate receiving an input RF signal and itssource coupled to one end of an inductor 552 a. The other end ofinductor 552 a is coupled to circuit ground. A cascode transistor 556 ahas its source coupled to the drain of gain transistor 554 a, its gatereceiving a first enable control signal (Venb1) for low-band, and itsdrain coupled to an output of amplifier circuit 550 a.

Amplifier circuit 550 b for mid-band includes a gain transistor 554 b, acascode transistor 556 b, and an inductor 552 b, which are coupled insimilar manner as gain transistor 554 a, cascode transistor 556 a, andinductor 552 a in amplifier circuit 550 a for low-band. Amplifiercircuit 550 c for high-band includes a gain transistor 554 c, a cascodetransistor 556 c, and an inductor 552 c, which are coupled in similarmanner as gain transistor 554 a, cascode transistor 556 a, and inductor552 a in amplifier circuit 550 a for low-band. Inductors 552 a, 552 band 552 c may be designed to provide good performance for low-band,mid-band, and high-band, respectively. The drains of cascode transistors556 a, 556 b, and 556 c are coupled to load circuits 570 a, 570 b and570 c, respectively, which may comprise transformers (e.g., as shown inFIG. 4A) and/or other circuits. Load circuits 570 a, 570 b and 570 c maybe designed to provide good performance for low-band, mid-band, andhigh-band, respectively.

FIG. 6 shows a schematic diagram of an exemplary design of an omni-bandLNA 640 without a source degeneration inductor. Omni-band LNA 640 mayalso be used for any one of LNAs 340 in FIG. 3. In the exemplary designshown in FIG. 6, omni-band LNA 640 includes a common gain transistor 654and three cascode transistors 656 a, 656 b, and 656 c for low-band,mid-band, and high-band, respectively. Gain transistor 654 has its gatereceiving an input RF signal (RFin) and its source coupled to circuitground. Cascode transistor 656 a has its source coupled to the drain ofgain transistor 654, its gate receiving a first enable control signal(Venb1) for low-band, and its drain coupled to a load circuit 670 a forlow-band. Cascode transistor 656 b has its source coupled to the drainof gain transistor 654, its gate receiving a second enable controlsignal (Venb2) for mid-band, and its drain coupled to a load circuit 670b for mid-band. Cascode transistor 656 c has its source coupled to thedrain of gain transistor 654, its gate receiving a third enable controlsignal (Venb3) for high-band, and its drain coupled to a load circuit670 c for high-band. Load circuits 670 a, 670 b and 670 c may comprisetransformers (e.g., as shown in FIG. 4A) and/or other circuits. Loadcircuits 670 a, 670 b and 670 c may be designed to provide goodperformance for low-band, mid-band, and high-band, respectively.

FIG. 7 shows a schematic diagram of an exemplary design of an omni-bandLNA 442 with a shared source degeneration inductor and feedback.Omni-band LNA 442 may also be used for any one of LNAs 340 in FIG. 3. Inthe exemplary design shown in FIG. 7, omni-band LNA 442 includes threeamplifier circuits 450 a, 450 b and 450 c for low-band, mid-band, andhigh-band, respectively, as described above for FIG. 4A. Omni-band LNA442 further includes a feedback circuit 460 coupled between the drainsof cascode transistors 456 a, 456 b and 456 c and the gates of gaintransistors 454 a, 454 b and 454 c, i.e., between the common input andthe outputs of amplifier circuits 450 a, 450 b and 450 c.

In the exemplary design shown in FIG. 7, feedback circuit 460 includesswitches 462 a, 462 b, and 462 c, a resistor 464, and a capacitor 466.Resistor 464 and capacitor 466 are coupled in series, with the bottomterminal of capacitor 466 being coupled to the gates of gain transistors454 a, 454 b and 454 c. Switches 462 a, 462 b, and 462 c have oneterminal coupled to resistor 464 and the other terminal coupled to thedrains of cascode transistors 456 a, 456 b and 456 c, respectively.Switches 462 a, 462 b, and 462 c may each be closed to connect feedbackcircuit 460 to its associated cascode transistor 456 and may be openedto disconnect feedback circuit 460 from the associated cascodetransistor 456. Feedback circuit 460 may also include one or more activecircuits such as a transistor.

In an exemplary design, feedback circuit 460 may be enabled and used forlow-band to provide input power match. For mid-band and high-band,feedback circuit 460 may be disabled, and source degeneration inductor452 may be used for input power match. Feedback circuit 460 may also beused in other manners.

Feedback circuit 460 may help with input matching for omni-band LNA 442.Feedback circuit 460 may also improve the linearity of amplifiercircuits 450 a, 450 b and/or 450 c. Each amplifier circuit 450 may belinearized by (i) both source degeneration inductor 452 and feedbackcircuit 460 when associated switch 462 is closed or (ii) only sourcedegeneration inductor 452 when associated switch 462 is opened. Theimproved linearity with feedback circuit 460 may allow a smallerinductor 452 to be used to obtain the desired linearity.

FIG. 8 shows a schematic diagram of an exemplary design of an omni-bandLNA 840 with a tunable matching circuit 830. Omni-band LNA 840 may beimplemented based on any of the omni-band LNA designs described above.Omni-band LNA 840 includes an input that receives an input RF signal(RFin) and K outputs that provide output RF signals (RFout1 to RFoutK)for K band groups, where K may be any integer value greater than one.Tunable matching circuit 830 is coupled to the input of omni-band LNA840 and performs input matching for LNA 840. Matching circuit 830receives a received RF signal (RFrx) and provides the input RF signal toomni-band LNA 840. K load circuits 870 a to 870 k are coupled to the Koutputs of omni-band LNA 840 and are designed for K band groups. Eachload circuit 870 may comprise a transformer (e.g., as shown in FIG. 4A)and/or other circuit components.

Tunable matching circuit 830 may be implemented in various manners. Someexemplary designs of tunable matching circuit 830 are described below.

FIG. 9A shows an exemplary design of a tunable matching circuit 830 abased on an L topology. The L topology includes a series circuitcomponent coupled to a shunt circuit component. A series circuitcomponent is a circuit component connected between two nodes. A shuntcircuit component is a circuit component connected between a node andcircuit ground. A circuit component may be an inductor, a capacitor, aresistor, etc. Matching circuit 830 a includes (i) a series inductor 912coupled between the input and output of matching circuit 830 a and (ii)a tunable shunt capacitor 914 coupled between the output of matchingcircuit 830 a and circuit ground.

FIG. 9B shows an exemplary design of a tunable matching circuit 830 bbased on the L topology. Matching circuit 830 b includes (i) a tunableseries capacitor 922 coupled between the input and output of matchingcircuit 830 b and (ii) a shunt inductor 924 coupled between the outputof matching circuit 830 b and circuit ground.

FIG. 9C shows an exemplary design of a tunable matching circuit 830 cbased on an R topology. The R topology includes a shunt circuitcomponent coupled to a series circuit component. Matching circuit 830 cincludes (i) a tunable shunt capacitor 932 coupled between the input ofmatching circuit 830 c and circuit ground and (ii) a series inductor 934coupled between the input and output of matching circuit 830 c.

FIG. 9D shows an exemplary design of a tunable matching circuit 830 dbased on a Pi topology. The Pi topology includes a shunt circuitcomponent coupled to a series circuit component, which is coupled toanother shunt circuit component. Matching circuit 830 d includes (i) ashunt capacitor 942 coupled between the input of matching circuit 830 dand circuit ground, (ii) a series inductor 944 coupled between the inputand output of matching circuit 830 d, and (iii) a tunable shuntcapacitor 946 coupled between the output of matching circuit 830 d andcircuit ground.

FIG. 9E shows an exemplary design of a tunable matching circuit 830 ewith two R sections. Matching circuit 830 e includes (i) a shuntinductor 952 coupled between the input of matching circuit 830 e and theVDD supply, (ii) a series capacitor 954 coupled between the input ofmatching circuit 830 e and node E, (iii) a tunable shunt capacitor 956coupled between node E and circuit ground, and (iv) a series inductor958 coupled between node E and the output of matching circuit 830 e.

FIG. 9F shows an exemplary design of a tunable matching circuit 830 fbased on the Pi topology. Matching circuit 830 f includes (i) a shuntinductor 962 coupled between the input of matching circuit 830 f and theVDD supply, (ii) a series capacitor 964 coupled between the input andoutput of matching circuit 830 f, (iii) a tunable shunt capacitor 966coupled between the output of matching circuit 830 f and circuit ground,and (iv) a shunt inductor 968 coupled between the output of matchingcircuit 830 f and circuit ground.

A fixed matching circuit may also be implemented based on any of theexemplary designs shown in FIGS. 9A to 9F. In this case, each adjustablecircuit component (e.g., each adjustable capacitor) may be replaced witha fixed circuit component (e.g., a fixed capacitor).

Transformers for different band groups may be implemented in variousmanners. The primary and secondary coils of a transformer may beimplemented with various patterns to obtain the desired inductance andcoupling. The primary and secondary coils may also be fabricated on oneor more conductive layers.

FIG. 10 shows a top view of an exemplary design of three transformersfor three band groups. The three transformers may be used fortransformers 472 a to 472 c in FIG. 4A, load circuits 570 a to 570 c inFIG. 5, load circuits 670 a to 670 c in FIG. 6, or load circuits 870 ato 870 c in FIG. 8.

In the exemplary design shown in FIG. 10, a transformer for low-bandincludes a primary coil 1074 a formed in a spiral pattern on a firstconductive layer. A transformer for mid-band includes a primary coil1074 b formed in a spiral pattern inside of primary coil 1074 a on thefirst conductive layer. A transformer for high-band includes a primarycoil 1074 c formed in a spiral pattern inside of primary coil 1074 b onthe first conductive layer. A ground guard ring 1080 is located betweenprimary coils 1074 a and 1074 b and provides isolation between these twoprimary coils. A ground guard ring 1082 is located between primary coils1074 b and 1074 c and provides isolation between these primary coils.

In an exemplary design, secondary coils for the three transformers maybe arranged in a spiral pattern on a second conductive layer. Thesecondary coil for each transformer 1072 may be formed directlyunderneath the primary coil for that transformer.

FIG. 10 shows an exemplary design in which three primary coils 1074 a,1074 b and 1074 c for three transformers for three band groups areformed inside of one another, which may save space. In general, theprimary and secondary coils of the transformers for different bandgroups may be implemented with any layout, any pattern, and any numberof turns. The number of turns, the diameter of the turns, the width andheight of each coil, the spacing between the primary and secondary coilsfor each transformer, and/or other attributes of the two coils may beselected to obtain the desired inductance and quality factor (Q) foreach coil and the desired coupling coefficient between the coils. Thecoupling coefficient may be varied by controlling the placement of thecoils and/or the distance between the coils.

The stacked topology in FIG. 10 may allow the transformers to befabricated in a smaller area and may also result in better matchingbetween the two ends of the secondary coil for a differential design.Transformers may also be implemented with a side-by-side topology orother topologies. In general, different topologies, layout patterns, andfabrication techniques may provide different advantages for atransformer.

The omni-band amplifiers (e.g., LNAs) described herein may providevarious advantages. First, an omni-band amplifier can support a widefrequency range covering multiple band groups, which may be highlydesirable for new wireless devices that are required to support manybands in different band groups. Second, an omni-band amplifier may havegood performance for all supported band groups, e.g., via use of atransformer and source degeneration for each band group. Third, anomni-band amplifier may reduce the number of input/output (I/O) pins onan IC chip since a single I/O pin can provide an input RF signal tosupport multiple band groups. Fourth, an omni-band amplifier may providemore flexibility since each I/O pin can be configured to support anyband group. For example, an IC may include 20 omni-band LNAs and may beconfigured to support (i) 20 low-band receivers, or (ii) 10 low-bandreceivers, 5 mid-band receivers, and 5 high-band receivers, or (iii) 10mid-band receivers and 10 high-band receivers, or (iv) some othercombination of receivers. The omni-band amplifiers may have otheradvantages.

In an exemplary design, an apparatus (e.g., a wireless device, an IC, acircuit module, etc.) may include at least one gain transistor and aplurality of cascode transistors for a plurality of band groups. The atleast one gain transistor (e.g., gain transistors 454 in FIG. 4A) mayreceive an input RF signal and may have the input(s) coupled together.The plurality of cascode transistors (e.g., cascode transistors 456) maybe coupled to the at least one gain transistor and may provide an outputRF signal for one of the plurality of band groups. The plurality of bandgroups may include low-band, mid-band, and/or high-band. Each band groupmay cover a plurality of bands.

In an exemplary design that is shown in FIG. 4A, the at least one gaintransistor may comprise a plurality of gain transistors (e.g., gaintransistors 454) for the plurality of band groups. One of the pluralityof gain transistors and one of the plurality of cascode transistors maybe enabled to amplify the input RF signal and provide the output RFsignal for the selected band group. In an exemplary design, theplurality of gain transistors may have different transistor sizes and/ordifferent bias currents. In an exemplary design, the apparatus mayfurther comprise an inductor (e.g., inductor 452 in FIG. 4A) having aplurality of taps coupled to the plurality of gain transistors andcircuit ground. In another exemplary design, the apparatus may furthercomprise a plurality of inductors (e.g., inductors 552 in FIG. 5)coupled between the plurality of gain transistors and circuit ground.

In another exemplary design that is shown in FIG. 6, the at least onegain transistor may comprise a single gain transistor (e.g., gaintransistor 654) coupled to the plurality of cascode transistors. Thisgain transistor may have its source coupled directly to circuit ground(e.g., as shown in FIG. 6) or to a source degeneration inductor.

In an exemplary design, the apparatus may include a feedback circuit(e.g., feedback circuit 460 in FIG. 7) coupled between at least one ofthe plurality of cascode transistors and the at least one gaintransistor. The feedback circuit may comprise a resistor, or acapacitor, or a transistor, or some other circuit component, or acombination thereof. The feedback circuit may be closed around aselected amplifier circuit, e.g., between a cascode transistor and again transistor for the selected amplifier circuit.

In an exemplary design, the apparatus may further comprise a tunablematching circuit (e.g., tunable matching circuit 830 in FIG. 8) coupledto the at least one gain transistor. The tunable matching circuit mayreceive a received RF signal and provide the input RF signal. Thetunable matching circuit may comprise at least one adjustable circuitcomponent (e.g., an adjustable capacitor).

In an exemplary design, the apparatus may further comprise a pluralityof transformers (e.g., transformers 472 in FIG. 4A) coupled to theplurality of cascode transistors. Each of the plurality of transformersmay be used for one of the plurality of band groups.

In an exemplary design, the at least one gain transistor may comprise afirst gain transistor for a first band group and a second gaintransistor for a second band group. The plurality of cascode transistorsmay comprise a first cascode transistor for the first band group and asecond cascode transistor for the second band group. The first gaintransistor may be coupled to the first cascode transistor. The secondgain transistor may be coupled to the second cascode transistor. Aninductor may be coupled between the first gain transistor and circuitground and may comprise a tap coupled to the second gain transistor. Afirst transformer for the first band group may be coupled to the firstcascode transistor. A second transformer for the second band group maybe coupled to the second cascode transistor. The first transformer maycomprise a first primary coil formed on a conductive layer. The secondtransformer may comprise a second primary coil formed within the firstprimary coil on the conductive layer (e.g., as shown in FIG. 10).

In an exemplary design, the at least one gain transistor may furthercomprise a third gain transistor for a third band group. The pluralityof cascode transistors may further comprise a third cascode transistorfor the third band group. The third gain transistor may be coupled tothe third cascode transistor. A third transformer for the third bandgroup may be coupled to the third cascode transistor.

FIG. 11 shows an exemplary design of a process 1100 for performingsignal amplification. An input RF signal may be amplified with one of atleast one gain transistor to obtain an amplified signal (block 1112).The amplified signal may be buffered with one of a plurality of cascodetransistors for a plurality of band groups to obtain an output RF signalfor one of the plurality of band groups (block 1114). The source of theone gain transistor may be degenerated with an inductor coupled to theat least one gain transistor (block 1116). The output RF signal may becoupled with one of a plurality of transformers for the plurality ofband groups to obtain an amplified RF signal (block 1118).

The omni-band amplifiers described herein may be implemented on an IC,an analog IC, an RFIC, a mixed-signal IC, an ASIC, a printed circuitboard (PCB), an electronic device, etc. The omni-band amplifiers mayalso be fabricated with various IC process technologies such ascomplementary metal oxide semiconductor (CMOS), N-channel MOS (NMOS),P-channel MOS (PMOS), bipolar junction transistor (BJT), bipolar-CMOS(BiCMOS), silicon germanium (SiGe), gallium arsenide (GaAs),heterojunction bipolar transistors (HBTs), high electron mobilitytransistors (HEMTs), silicon-on-insulator (SOI), etc.

An apparatus implementing an omni-band amplifier described herein may bea stand-alone device or may be part of a larger device. A device may be(i) a stand-alone IC, (ii) a set of one or more ICs that may includememory ICs for storing data and/or instructions, (iii) an RFIC such asan RF receiver (RFR) or an RF transmitter/receiver (RTR), (iv) an ASICsuch as a mobile station modem (MSM), (v) a module that may be embeddedwithin other devices, (vi) a receiver, cellular phone, wireless device,handset, or mobile unit, (vii) etc.

In one or more exemplary designs, the functions described may beimplemented in hardware, software, firmware, or any combination thereof.If implemented in software, the functions may be stored on ortransmitted over as one or more instructions or code on acomputer-readable medium. Computer-readable media includes both computerstorage media and communication media including any medium thatfacilitates transfer of a computer program from one place to another. Astorage media may be any available media that can be accessed by acomputer. By way of example, and not limitation, such computer-readablemedia can comprise RAM, ROM, EEPROM, CD-ROM or other optical diskstorage, magnetic disk storage or other magnetic storage devices, or anyother medium that can be used to carry or store desired program code inthe form of instructions or data structures and that can be accessed bya computer. Also, any connection is properly termed a computer-readablemedium. For example, if the software is transmitted from a website,server, or other remote source using a coaxial cable, fiber optic cable,twisted pair, digital subscriber line (DSL), or wireless technologiessuch as infrared, radio, and microwave, then the coaxial cable, fiberoptic cable, twisted pair, DSL, or wireless technologies such asinfrared, radio, and microwave are included in the definition of medium.Disk and disc, as used herein, includes compact disc (CD), laser disc,optical disc, digital versatile disc (DVD), floppy disk and blu-ray discwhere disks usually reproduce data magnetically, while discs reproducedata optically with lasers. Combinations of the above should also beincluded within the scope of computer-readable media.

The previous description of the disclosure is provided to enable anyperson skilled in the art to make or use the disclosure. Variousmodifications to the disclosure will be readily apparent to thoseskilled in the art, and the generic principles defined herein may beapplied to other variations without departing from the scope of thedisclosure. Thus, the disclosure is not intended to be limited to theexamples and designs described herein but is to be accorded the widestscope consistent with the principles and novel features disclosedherein.

What is claimed is:
 1. An apparatus comprising: at least one gaintransistor configured to receive an input radio frequency (RF) signal;and a plurality of cascode transistors for a plurality of band groupscoupled to the at least one gain transistor and configured to provide anoutput RF signal for one of the plurality of band groups.
 2. Theapparatus of claim 1, the at least one gain transistor comprising aplurality of gain transistors for the plurality of band groups.
 3. Theapparatus of claim 2, further comprising: an inductor comprising aplurality of taps coupled to the plurality of gain transistors andcircuit ground.
 4. The apparatus of claim 2, further comprising: aplurality of inductors coupled between the plurality of gain transistorsand circuit ground.
 5. The apparatus of claim 1, the at least one gaintransistor comprising a single gain transistor coupled to the pluralityof cascode transistors.
 6. The apparatus of claim 1, further comprising:a feedback circuit coupled between at least one of the plurality ofcascode transistors and the at least one gain transistor.
 7. Theapparatus of claim 1, further comprising: a tunable matching circuitcoupled to the at least one gain transistor and configured to receive areceived RF signal and provide the input RF signal.
 8. The apparatus ofclaim 1, further comprising: a plurality of transformers coupled to theplurality of cascode transistors, each of the plurality of transformersbeing used for one of the plurality of band groups.
 9. The apparatus ofclaim 1, the at least one gain transistor comprising a first gaintransistor for a first band group and a second gain transistor for asecond band group, and the plurality of cascode transistors comprising afirst cascode transistor for the first band group and a second cascodetransistor for the second band group.
 10. The apparatus of claim 9,further comprising: an inductor coupled between the first gaintransistor and circuit ground and comprising a tap coupled to the secondgain transistor.
 11. The apparatus of claim 9, further comprising: afirst transformer for the first band group coupled to the first cascodetransistor, and a second transformer for the second band group coupledto the second cascode transistor.
 12. The apparatus of claim 11, thefirst transformer comprising a first primary coil formed on a conductivelayer, and the second transformer comprising a second primary coilformed within the first primary coil on the conductive layer.
 13. Theapparatus of claim 9, the at least one gain transistor furthercomprising a third gain transistor for a third band group, and theplurality of cascode transistors further comprising a third cascodetransistor for the third band group.
 14. The apparatus of claim 2, theplurality of gain transistors having different transistor sizes, ordifferent bias currents, or both.
 15. The apparatus of claim 1, theplurality of band groups including at least one of low-band, mid-band,and high-band.
 16. A method comprising: amplifying an input radiofrequency (RF) signal with one of at least one gain transistor to obtainan amplified signal; and buffering the amplified signal with one of aplurality of cascode transistors for a plurality of band groups toobtain an output RF signal for one of the plurality of band groups. 17.The method of claim 16, further comprising: degenerating a source of theone gain transistor with an inductor coupled to the at least one gaintransistor.
 18. The method of claim 16, further comprising: coupling theoutput RF signal with one of a plurality of transformers for theplurality of band groups to obtain an amplified RF signal.
 19. Anapparatus comprising: at least one amplifying means configured toreceive an input radio frequency (RF) signal; and a plurality ofbuffering means for a plurality of band groups coupled to the at leastone amplifying means and configured to provide an output RF signal forone of the plurality of band groups.
 20. The apparatus of claim 19, theat least one amplifying means comprising a plurality of amplifying meansfor the plurality of band groups, the apparatus further comprising:source degeneration means comprising a plurality of taps coupled to theplurality of amplifying means and circuit ground.
 21. The apparatus ofclaim 19, further comprising: a plurality of transforming means coupledto the plurality of buffering means, each of the plurality oftransforming means being used for one of the plurality of band groups.